The identification of cracks in the metal structure of lifting machinery is a new direction for infrared thermal imaging detection technology. In this study, the detection principle of pulsed infrared thermal imaging was introduced, and a pulsed infrared thermal imaging detection system was designed; the experimental platform was constructed on the basis of these. Median filtering and Butterworth low-pass filtering were used to process the images collected in the experiment. To address the problem of blurring at the edges of the defects after processing the above algorithms, a Butterworth band-pass filtering algorithm was proposed. After threshold segmentation and edge detection, the defect contour feature was extracted, and using the conversion relationship between the actual size of the flat specimen and the contour feature image pixels, the recognition accuracy of the crack defect was finally obtained. The comparison and verification demonstrated that the pulsed infrared thermal imaging technology can meet the requirements of crack defect detection in crane metal structures.